1. Field of the Invention
Generally, the field of invention concerns medical imaging and more precisely, a method for generating medical images to highlight suspect regions in a tissue matrix. These images are generated from two-dimensional or three-dimensional medical images of the same object and are combined with the results from a system to detect radiologically suspect regions in said object. The method to generate medical images is used to detect lesions of cancerous type, notably breast lesions.
2. Description of Related Art
For the diagnosis of breast cancer, radiology is generally used to obtain an image of the inside of the breast. A two-dimensional (2D) radiological image shows a projection of a tissue matrix, e.g. a breast for breast cancer diagnosis, onto a plane formed by a detector, from a radiation source. The radiological image is generally obtained by placing the object of interest between the X-ray emitting source and the X-ray detector, so that the rays reach the detector after passing through the object. The radiological image is then created from data provided by the detector, and represents the tissue matrix projected onto the detector in the direction of the X-rays.
In such a radiological image, an experienced practitioner can distinguish radiological signs indicating a potential problem, e.g. micro-calcifications or opacities in the case of mammography. However, a radiological image is derived from a two-dimensional projection of a three-dimensional tissue matrix. Tissue superimposition may mask radiological signs such as lesions, and under no circumstance is the true position of the radiological signs inside the object of interest known; the practitioner having no information on the position of the radiological signs in the direction of projection.
Tomosynthesis has recently been developed to address these issues; it allows a three-dimensional (3D) representation of an object of interest to be obtained in the form of a series of successive slices. These slices are reconstructed from projections of the object of interest at different angles. For this purpose, the object of interest is generally placed between an X-ray emitting source and an X-ray detector. The source and/or the detector are movable, which means that the projection direction of the object of interest onto the detector can be varied (typically over an angle range of 30°). In this manner, several projections of the object of interest are obtained at different angles, from which a 3D representation of the object of interest can be reconstructed, generally using a reconstruction method well known to the person skilled in the art, see for example document FR 2 872 659.
Therefore, when examining the tomosynthesis slices of an object of interest, a practitioner is able to detect radiological signs in the object of interest and to assess their position in three dimensions. However, practitioners have years of experience in the analysis of 2D radiological images (standard mammography), whereas the analysis of tomosynthesis slices has only just begun.
Therefore, a transition period is preferable. During this transition period, practitioners will have to analyze tomosynthesis slices of an object of interest accompanied by standard mammography images of one same object of interest, in order to gain experience and comfort in analysing 3D slices and comparing these with conventional 2D radiology images as part of a study on changes in radiological signs over time. From this perspective, research has been conducted to produce radiographic image acquisition systems to obtain radiological images and tomosynthesis slices of the same object of interest.
However, the practitioner will first look for a suspect region in the 2D radiological image before viewing the slices obtained by tomosynthesis. Thus, the problem relating to the superimposition of tissues in radiological images therefore remains.